Piper diospyrifolium Kunth.: Chemical analysis and antimicrobial (intrinsic and combined) activities

Inhibition of the morphological transition of Candida spp. by riparins I-IV

Candida spp. is an opportunistic pathogen capable of causing superficial to invasive infections. Morphological transition is one of the main virulence factors of this genus and, therefore, is an important variable to be considered in pharmacological interventions. Riparins I, II, III, and IV are alkamide-type alkaloids extracted from the unripe fruit of Aniba riparia, whose remarkable pharmacological properties were previously demonstrated. This work aimed to evaluate in silico and in vitro the inhibitory effects of Riparins on the morphological transition of Candida albicans, Candida tropicalis, and Candida krusei. Molecular docking was applied to analyze the inhibitory effects of riparins against proteins such as N-acetylglucosamine, CYP-51, and protein kinase A (PKA) using the Ramachandran plot. The ligands were prepared by MarvinSketch and Spartan software version 14.0, and MolDock Score and Rerank Score were used to analyze the affinity of the compounds. In vitro analyses were performed by culturing the strains in humid chambers in the presence of riparins or fluconazole (FCZ). The morphology was observed through optical microscopy, and the size of the hyphae was determined using the ToupView software. In silico analysis demonstrated that all riparins are likely to interact with the molecular targets: GlcNAc (>50%), PKA (>60%), and CYP-51 (>70%). Accordingly, in vitro analysis showed that these compounds significantly inhibited the morphological transition of all Candida strains. In conclusion, this study demonstrated that riparins inhibit Candida morphological transition and, therefore, can be used to overcome the pathogenicity of this genus.

Chemical Profile and Biological Activities Of Piper mikanianum (Kunth) Steud Essential Oil for Development and Improvement of Oral Rinse

INTRODUCTION

Studies prove that the use of medicinal plants is a custom carried out by man since ancient times, the evolution of the pharmaceutical industry makes more people consume more natural products. Currently, we can observe that mouthwashes containing natural compounds have shown a growth in demand in the markets and in the professional community.

OBJECTIVE

The present study aims to carry out the chemical characterization and microbiological potential of Piper mikanianum (Kunth) Steud essential oil (EOPm), providing data that allows the development of a low-cost mouthwash formulation aimed at vulnerable communities.

METHODS

The evaluation of the antibacterial activity and modulator of bacterial resistance was performed by the microdilution method to determine the minimum inhibitory concentration (MIC). The chemical components were characterized by gas chromatography coupled to mass spectrometry, identified 28 constituents, in which Safrole Phenylpropanoid is the major compound, representing 72.6 % of the total composition, followed by α-pinene (10.7 %), Limonene (2 %), β-caryophyllene (2 %), E-nerolidol (1.9 %), spathulenol (1.3 %) and camphene (1.1 %).

RESULTS

The EOPm showed a MIC minimum inhibitory concentration≥1024 μg/mL for all bacterial strains used in the tests. When the EOPm modulating activity combined with chlorhexidine, mouthwash, ampicillin, gentamicin and penicillin G was evaluated against bacterial resistance, the oil showed significant synergistic activity, reducing the MIC of the products tested in combination, in percentage between 20.6 % to 98 .4 %.

CONCLUSIONS

We recommend the expansion of tests with greater variation of EOPm concentration combinations and the products used in this study, as well as toxicity evaluation and in vivo tests, seeking the development of a possible low-cost mouthwash formulation accessible to the most vulnerable population.

UPLC-MS-ESI-QTOF Analysis and Antifungal Activity of Aqueous Extracts of Spondias tuberosa

This study aimed to identify the chemical composition of the Spondias tuberosa aqueous leaf and root extracts (EALST and EARST) and to evaluate their effect, comparatively, against opportunistic pathogenic fungi. Ultra-Performance Liquid Chromatography Coupled to a Quadrupole/Time of Flight System (UPLC-MS-ESI-QTOF) was employed for chemical analysis. Candida albicans and C. tropicalis standard strains and clinical isolates were used (CA INCQS 40006, CT INCQS 40042, CA URM 5974, and CT URM 4262). The 50% Inhibitory Concentration for the fungal population (IC₅₀) was determined for both the intrinsic action of the extracts and the extract/fluconazole (FCZ) associations. The determination of the Minimum Fungicidal Concentration (MFC) and the verification of effects over fungal morphological transitions were performed by subculture in Petri dishes and humid chambers, respectively, both based on micro-dilution. UPLC-MS-ESI-QTOF analysis revealed the presence of phenolic and flavonoid compounds. The association of the extracts with fluconazole, resulted in IC₅₀ values from 2.62 µg/mL to 308.96 µg/mL. The MFC of the extracts was ≥16,384 µg/mL for all tested strains, while fluconazole obtained an MFC of 8192 µg/mL against C. albicans strains. A reduction in MFC against CA URM 5974 (EALST: 2048 µg/mL and EARST: 1024 µg/mL) occurred in the extract/fluconazole association.

Lectins ConA and ConM extracted from Canavalia ensiformis (L.) DC and Canavalia rosea (Sw.) DC inhibit planktonic Candida albicans and Candida tropicalis

Lectins participate in the defense against microorganisms and in signaling the damage caused by pathogens to the cell surface and/or intracellular in plants. This study aims to analyze the antifungal potential of lectins extracted from seeds of Canavalia ensiformis (L.) DC and Canavalia rosea (Sw.) DC, against Candida albicans and Candida tropicalis. The antimicrobial tests were performed by microdilution against Candida spp. The test to verify the combined lectin/fluconazole effect was performed using subinhibitory concentrations of lectins and with antifungal ranging from 0.5 to 512 µg/mL. The ability to inhibit the morphological transition of Candida spp. was evaluated by microcultivation in a moist chamber. The results of the minimum inhibitory concentration revealed no antifungal activity against the tested strains. However, lectins modified the action of fluconazole, reducing the IC₅₀ of the drug against C. albicans. Lectins were also able to discretely modulate the morphological transition of the tested strains.

Anti-Candida Properties of Gossypium hirsutum L.: Enhancement of Fungal Growth, Biofilm Production and Antifungal Resistance

(1) Background: Candida is a genus of yeasts with notable pathogenicity and significant ability to develop antimicrobial resistance. Gossypium hirsutum L., a medicinal plant that is traditionally used due to its antimicrobial properties, has demonstrated significant antifungal activity. Therefore, this study investigated the chemical composition and anti-Candida effects of aqueous (AELG) and hydroethanolic (HELG) extracts obtained from the leaves of this plant. (2) Methods: The extracts were chemically characterized by UPLC–QTOF-MS/MS, and their anti-Candida activities were investigated by analyzing cell viability, biofilm production, morphological transition, and enhancement of antifungal resistance. (3) Results: The UPLC–QTOF-MS/MS analysis revealed the presence of twenty-one compounds in both AELG and HELG, highlighting the predominance of flavonoids. The combination of the extracts with fluconazole significantly reduced its IC₅₀ values against Candida albicans INCQS 40006, Candida tropicalis INCQS 40042, and C. tropicalis URM 4262 strains, indicating enhanced antifungal activity. About biofilm production, significant inhibition was observed only for the AELG-treated C. tropicalis URM 4262 strain in comparison with the untreated control. Accordingly, this extract showed more significant inhibitory effects on the morphological transition of the INCQS 40006 and URM 4387 strains of C. albicans (4) Conclusions: Gossypium hirsutum L. presents promising antifungal effects, that may be potentially linked to the combined activity of chemical constituents identified in its extracts.

Essential Oils from Piper caldense C. DC. and Piper xylosteoides (Kunth) Steud.: Seasonal Variation of the Chemical Composition and Antimicrobial Activity

The essential oils (EOs) chemical composition can be affected by several environmental factors, impacting their desired biological activities. In this sense, this work aimed to evaluate the seasonal variation of the chemical composition and antimicrobial activity of Piper caldense and Piper xylosteoides leaves EOs. Their chemical composition was determined by GC/MS and GC-FID analyses, resulting in the identification of eighty compounds. P. caldense EOs were mainly consisted of sesquiterpene hydrocarbons, whereas in P. xylosteoides EOs, monoterpene hydrocarbons were predominant. EOs from both species strongly inhibited B. subtilis (MIC=0.25 mg mL^-1 ), while only P. caldense EOs showed strong activity against S. aureus (MIC=0.50 mg mL^-1 ). P. caldense spring EO showed the broadest spectrum of antimicrobial action amongst all samples. For each species, PCA seasonally differentiated EOs chemical composition. In addition, as expected, PCA of all samples showed a distinction between the two species. This study has successfully demonstrated the importance of evaluating the seasonal variation of EOs chemical composition and antimicrobial activity in obtaining a product with the desired properties.

Chemical Constituents and Biological Activities of Croton heliotropiifolius Kunth

Croton heliotropiifolius Kunth (Euphorbiaceae), whose occurrence has already been registered in the most varied Brazilian biomes, is commonly found in the Chapada do Araripe, Ceará. The species is traditionally used to treat fungal, parasitic, and degenerative diseases. This study investigated the chemical composition and pharmacological potential (antioxidant, antifungal, antiparasitic, and cytotoxic) of an aqueous extract obtained from the roots of C. heliotropiifolius. Following a qualitative phytochemical screening, the chemical constituents were identified by ultra-efficiency liquid chromatography coupled witha quadrupole/time-of-flight system (UPLC-QTOF). The antioxidant potential was verified by thin-layer chromatography (TLC). The direct and combined antifungal activity of the extract against opportunistic Candida strains was investigated using the microdilution method. The minimal fungicidal concentration (MFC) was determined by subculture, while the modulation of the morphological transition (fungal virulence) was evaluated by light microscopy. The in vitro antiparasitic activity was analyzed using epimastigotes of Trypanosoma cruzi and promastigotes of Leishmania braziliensis and Leishmania infantum, while cytotoxicity was determined in cultures of mouse fibroblasts. The phytochemical analysis identified the presence of acids, terpenes, flavonoids, lignans, and alkaloids. Among these constituents, the presence of polar and non-polar phenolic compounds with known antioxidant action was highlighted. While the extract showed clinically ineffective antifungal effects, it could enhance the effectiveness of fluconazole, in addition to inhibiting the morphological transition associated with increased virulence in Candida strains. Although the extract showed low cytotoxicity against fibroblasts, it also had weak antiparasitic effects. In conclusion, Croton heliotropiifolius is a source of natural products with antifungal and antioxidant potential.

Antibiotic Potentiation of Natural Products: A Promising Target to Fight Pathogenic Bacteria

Pathogenic microorganisms should be considered as the number one foe of human, as witnessed by recent outbreaks of coronavirus disease (COVID-19) and with bacteria no longer sensitive to existing antibiotics. The resistance of pathogenic bacteria and deaths attributable to bacterial infections is increasing exponentially. Bacteria used different mechanisms to counterattack to existing antibiotics, namely (i) enzymatic inhibition, (ii) penicillin-binding protein modification, (iii) porin mutations, (iv) efflux pumps and (v) molecular modifications of antibiotic targets. Developing new antibiotics would be time-consuming to address such a situation, thus one of the promising approaches is by potentiating existing antibiotics. Plants used synergism to naturally defend and protect themselves from microbes. Using the same strategy, several studies have shown that the combinations of natural products and antibiotics could effectively prolong the lifespan of existing antibiotics and minimize the impact and emergence of antibiotic resistance. Combining essential oils constituents, namely uvaol, ferruginol, farnesol and carvacrol, with antibiotics, have proved to be efficient efflux pump inhibitors. Plant-derived compounds such as gallic acid and tannic acid are effective potentiators of various antibiotics, including novobiocin, chlorobiocin, coumermycin, fusidic acid, and rifampicin, resulting in a 4-fold increase in the potencies of these antibiotics. Several lines of research, as discussed in this review, have demonstrated the effectiveness of natural products in potentiating existing antibiotics. For this reason, the search for more efficient combinations should be an ongoing process with the aim to extend the life of the ones that we have and may preserve the life for the ones that are yet to come.

Antifungal Effect of Liposomal α-Bisabolol and When Associated with Fluconazole

Fungal pathologies caused by the genus Candida have increased in recent years due to the involvement of immunosuppressed people and the advance of resistance mechanisms acquired by these microorganisms. Liposomes are nanovesicles with lipid bilayers in which they store compounds. α-Bisabolol is a sesquiterpene with proven biological activities, and in this work it was tested alone in liposomes and in association with Fluconazole in vitro to evaluate the antifungal potential, Fluconazole optimization, and virulence inhibitory effect in vitro. Antifungal assays were performed against standard strains of Candida albicans, Candida tropicalis, and Candida krusei by microdilution to identify the IC50 values and to obtain the cell viability. The Minimum Fungicidal Concentration (MFC) was performed by subculturing on the solid medium, and at their subinhibitory concentration (Matrix Concentration (MC): 16,384 µg/mL) (MC/16), the compounds, both isolated and liposomal, were associated with fluconazole in order to verify the inhibitory effect of this junction. Tests to ascertain changes in morphology were performed in microculture chambers according to MC concentrations. Liposomes were characterized from the vesicle size, polydispersity index, average Zeta potential, and scanning electron microscopy. The IC50 value of the liposomal bisabolol associated with fluconazole (FCZ) was 2.5 µg/mL against all strains tested, revealing a potentiating effect. Liposomal bisabolol was able to potentiate the effect of fluconazole against the CA and CT strains by reducing its concentration and completely inhibiting fungal growth. α-Bisabolol in liposomal form inhibited the morphological transition in all strains tested at a concentration of MC/8. The liposomes were homogeneous, with vesicles with diameters of 203.8 nm for the liposomal bisabolol and a surface charge potential of −34.2 mV, conferring stability to the nanosystem. Through scanning microscopy, the spherical shapes of the vesicles were observed.

Phytochemical characterization and inhibition of Candida sp. by the essential oil of Baccharis trimera (Less.) DC

This study aimed to investigate the chemical composition and antifungal potential of the essential oil of Baccharis trimera (Less.) DC. against Candida strains. The half maximal inhibitory concentration (IC₅₀) was assessed by the microdilution method using the essential oil at a concentration range of 8192 to 8 μg/mL. The minimum fungicide concentration (MFC) was determined by subculture in solid medium. The ability of the essential oil to modulate the activity of antifungals was determined in wells treated simultaneously with the oil at a subinhibitory concentration (MFC/16) and fluconazole (FCZ). The fungal morphology was analyzed by microscopy. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the chemical composition. The essential oil presented an CI₅₀ of 11.24 and 1.45 μg/mL, which was found to potentiate the effect of FCZ against Candida albicans. On the other hand, this combined treatment resulted in antagonism against Candida tropicalis and no evident modulation against Candida krusei was observed. The essential oil significantly inhibited hyphae growth. However, with a MFC ≥ 16,384 μg/mL, it is assumed that it has a fungistatic action. The antifungal properties demonstrated in this study might be related to the presence of sesquiterpenes and monoterpenes, and the interaction between them. In conclusion, Baccharis trimera showed promising anti-Candida effects, in addition to potentiating the activity of FCZ against Candida albicans, affecting its morphological transition. Therefore, this species constitutes a source of chemical compounds with the potential to be used in the combat of fungal infections.

Antifungal Properties of Nerolidol-Containing Liposomes in Association with Fluconazole

(1) Background: Infections by Candida species represent a serious threat to the health of immunocompromised individuals. Evidence has indicated that nerolidol has significant antifungal properties. Nonetheless, its use is restricted due to a low water solubility and high photosensitivity. The incorporation into liposomes may represent an efficient alternative to improve the physicochemical and biopharmaceutical properties of this compound. The present study aimed to characterize the antifungal properties of liposomal nerolidol, alone or in combination with fluconazole. Of note, this is the first study reporting the antifungal activity of liposomal nerolidol and its potentiating effect in association with fluconazole. (2) Methods: The Inhibitory Concentration 50%-IC₅₀ and minimum fungicide concentrations (MFC) of the substances against Candida albicans (CA), Candida tropicalis (CT), and Candida krusei (CK) were established by subculture in a solid medium. To evaluate the antifungal-enhancing effect, the MFC of fluconazole was determined in the presence or absence of subinhibitory concentrations of nerolidol (free or liposomal). The analysis of fungal dimorphism was performed through optical microscopy and the characterization of liposomes was carried out considering the vesicular size, polydispersion index, and zeta medium potential, in addition to a scanning electron microscopy analysis. (3) Results: The physicochemical characterization revealed that liposomes were obtained as homogenous populations of spherical vesicles. The data obtained in the present study indicate that nerolidol acts as an antifungal agent against Candida albicans and Candida tropicalis, in addition to potentiating (only in the liposomal form) the effect of fluconazole. However, the compound had little inhibitory effect on fungal dimorphism. (4) Conclusions: The incorporation of nerolidol into liposomes improved its antifungal-modulating properties.

UPLC-MS-ESI-QTOF Analysis and Antifungal Activity of the Spondias tuberosa Arruda Leaf and Root Hydroalcoholic Extracts

The aim of this study was to identify and evaluate the chemical compositions and effects of the S. tuberosa leaf and root hydroalcoholic extracts (HELST and HERST) against different strains of Candida. Chemical analysis was performed by Ultra-Performance Liquid Chromatography Coupled to Quadrupole/Time of Flight System (UPLC-MS-ESI-QTOF). The Inhibitory Concentration of 50% of the growth (IC₅₀₎ as well as the intrinsic and combined action of the extracts with the antifungal fluconazole (FCZ) were determined by the microdilution method while the minimum fungicidal concentrations (MFCs) and the effect on fungal morphological transitions were analyzed by subculture and in humid chambers, respectively. From the preliminary phytochemical analysis, the phenols and flavonoids were the most abundant. The intrinsic IC₅₀ values for HELST ranged from 5716.3 to 7805.8 µg/mL and from 6175.4 to 51070.9 µg/mL for the HERST, whereas the combination of the extracts with fluconazole presented IC₅₀ values from 2.65 to 278.41 µg/mL. The MFC of the extracts, individually, for all the tested strains was ≥16384 µg/mL. When fluconazole was combined with each extract, the MFC against CA URM 5974 was reduced (HELST: 2048 and HERST: 4096 µg/mL). Synergism was observed against standard C. albicans (CA) and C. tropicalis (CT) strains and with the root extract against the CT isolate. The leaf extract inhibited the morphological transition of all strains while the root extract inhibited only CT strains.